Information on Chesapeake Bay Retriever Genetics, Health, and Pedigrees

What Is Hip Dysplasia?


The canine hip joint is a "ball and socket" joint. "Dysplasia" is a word meaning "poor development". Hip dysplasia is a developmental condition of the hip joint. It causes the femoral head ("ball" of the hip joint), which normally sits snugly in the acetabulum ("socket" of the hip joint), to show some degree of deformation which can lead to arthritis.  This deformation can take different forms, depending on what genes are involved with creating that individual dog's hip dysplasia. It may be a shallow acetabulum, or a flattening of the femoral head. The femoral head itself may be deformed. Or the femoral neck (the narrow part just under the head or "ball" part of the joint) may be shortened and thickened. Any one of these may lead to hip dysplasia; a dog may have several conditions in its hips that create dysplasia. Dogs that have the genes that predispose them to hip dysplasia will develop the disease. Some environmental factors (such as weight, exercise, or exposure to extreme cold weather) can contribute to the severity of the disease. However, a dog must have the genes in order to develop the disease. Environmental factors alone cannot cause hip dysplasia.

Hip dysplasia is a polygenic disease. It is not yet known how many genes contribute to this condition. Because possibly many genes are involved, it is very difficult to completely remove the genes for bad hips from a population. We use x-rays to determine if a dog appears to be dysplastic or not. This is known as a phenotypic evaluation; we are not able to identify any genes, but only the effects of those genes. If a dog has enough of the genes for hip dysplasia, it will show up as dysplastic on x-ray. X-rays are evaluated by a panel of experts in canine orthopedics and radiography, and given a score or rating. Orthopedic Foundation for Animals (OFA) is the hip scoring system most used by Chessie breeders. Different organizartions in various countries use different ways of reporting the results of hip x-rays. Click here to see a chart comparing the various hip scoring schemes.

Chesapeakes rank 29th out of 164 breeds that OFA is tracking; this places Chessies among the breeds most prone to develop hip dysplasia. Statistics show that Chesapeakes radiograph as dysplastic 20 percent of the time. This means that at least one-in-five Chesapeakes is dysplastic. Because x-rays are taken and reviewed by a dog’s regular vet before being sent in to OFA, many times the owner chooses not to send them in to OFA for evaluation if it is obvious that the dog will not pass. For this reason, OFA recommends "ballparking" a much higher rate of dysplasia in any breed. In Chessies, this means the actual hip dysplasia rate may be as high as one-in four, or even one-in-three. We really do not know.

Hip dysplasia can affect only one hip. Unilateral dysplasia is not uncommon in Chessies. Because veterinarians (like everyone else) are either right- or left-handed, it is sometimes a matter of positioning; if the vet pulls harder on their dominant-handed side, this can make the x-ray appear slightly off. OFA will re-evaluate a new set of x-rays at any time. There is no limit to the number of times you can x-ray your dog and have the x-rays resubmitted to OFA.

Not all dogs who appear dysplastic on x-rays will show symptoms. Many Chesapeakes who radiograph dysplastic are only mildly so. Because the breed has a high tolerance for pain, many of these dogs may never show signs of lameness. This works both ways; a dog may be able to have a long working life even when it has dysplasia. On the other hand, assuming a dog is OK without x-rays because "He has never been lame" is also not correct. The only way to accurately diagnose hip dysplasia is through x-rays.

When should you x-ray your Chessie? The OFA does not certify dogs until they have passed their second birthday (24 months). However, you can have preliminary x-rays done at any age and evaluated by OFA. Your dog will not receive a number, but you can see where things are at with your dog’s hips. Because of their unique hindquarters construction (Chessies are as high as or higher in the hips than at the shoulder), Chessies develop much more slowly than many other breeds. This means that Chessies may not tighten up by age two. If a dog x-rays as dysplastic at two, and you feel may be a valuable addition to your breeding program, it is always worthwhile waiting six months to a year to redo the x-rays. This is especially true for males, who are larger and slower to mature than females. Females should not be x-rayed around their season, or for 3 months after. This is because hormones that control seasons and false pregnancies are present in all fertile bitches, whether they have been bred or not. These hormones can "loosen" a bitch’s hips, and cause her to fail an OFA x-ray. Wait until 3-4 months after her season to do x-rays.

Positioning is very important. Again, because of their unique hindquarters construction, and heavy musculature, Chessies can be difficult to position. Sedation is recommended, unless you are working with a veterinarian who has considerable experience x-raying hips on athletic dogs without anaesthesia or sedation. Modern sedatives work very well, and are very safe. If you choose to go without sedation, be prepared to redo the films if your dog does not pass the first time. Study the diagrams on positioning on the OFA Application for Hip/Elbow Dysplasia Database, to be sure you understand how a dog may appear to be dysplastic when the positioning is even just a little bit off. Do not be afraid to go elsewhere for a different set of x-rays. Not all vets are good at positioning Chessie hips.

OFA is not the only hip certifying organization. Ontario Veterinary College in Canada does hip and elbow certifications for manyCanadian dog breeders. Penn Hip also offers a program with a different emphasis for reducing hip dysplasia in breeds. The Baker Institute at Cornell University Veterinary Teaching Hospital is conducting continuing research into hip dysplasia and its causes. Here is a link to a brochure outlining a relatively new diagnostic technique for hip dysplasia developed at Baker. Europe and the UK each have their own hip scoring organizations as well. The British Veterinary Association tracks results of hip, elbow, and eye checks for dogs in the United Kingdom, Australia, and New Zealand. Many European countries use the FCI scoring method. You will see these scores on pedigrees of overseas dogs in the database.

Here is an interesting article regarding a study done on hip dysplasia in the Boykin Spaniel. Like Chessies, Boykins are considered a dysplastic breed. Chessies are one of the root breeds used to create the Boykin Spaniel breed. Therefore, it is not surprising that both breeds have similar issues with hip dysplasia.

Abstract of article comparing OFA and BVA hip schemes